1. Field
Example embodiments relate to an image pick-up device. More particularly, example embodiments relate to an image sensor capable of securing saturation electrons and an image sensing system including the image sensor.
2. Description of the Related Art
Image sensors are semiconductor devices that convert an optical image into an electrical signal, and may be roughly classified into charge coupled device (CCD) image sensors and CMOS image sensors (CISs).
A conventional CIS may include a photo sensitive device (PSD) in order to sense an image for each unit pixel. For example, a unit pixel may include a PSD and transistors for transmitting a signal sensed by the PSD, e.g., a transfer transistor, a reset transistor, a drive transistor, etc.
However, a decrease in a size of an image sensor may decrease sensitivity of the image sensors, so it may be difficult to secure saturation electrons. For example, as a size of a unit pixel of an image sensor decreases, an absolute area of a PSD in the unit pixel, e.g., an area of a PSD of each unit pixel, may decrease. The decrease of the area of the PSD may decrease the sensitivity of the image sensor and the saturation electrons. This may lead, e.g., to degradation of the quality of image of the image sensor.